Packaging pouches are typically made on form, fill and seal machines. For example, using a vertical form, fill and seal machine, a flat web of synthetic thermoplastic film is unwound from a roll and formed into a continuous tube in a tube forming operation, by sealing the longitudinal edges of the film together to form a lap seal or a fin seal. The tube thus formed is pulled vertically downwards to a filling station. The tube is then collapsed across a transverse cross-section of the tube, the position of the cross-section being at a sealing device below the filling station. A transverse heat seal is made by the sealing device at the collapsed portion of the tube, thus making an airtight seal across the tube. The sealing device generally comprises a pair of jaws.
After making the transverse seal, but before the jaws of the sealing device are opened, a quantity of material to be packaged, for example a liquid, is caused to enter the tube at the filling station, and to fill the tube upwardly from the aforementioned transverse seal. The tube is then caused to move downwardly a predetermined distance. This movement may be under the influence of the weight of the material in the tube, or it may be caused by pulling or mechanically driving the tube The jaws of the sealing device are closed again, thus collapsing the tube at a second transverse section. The second transverse section may be above, usually just above the air/material interface in the tube, or the second transverse section may be below the air/material interface. The sealing device seals and severs the tube transversely at the second transverse section. The material filled portion of the tube is now in the form of a pillow shaped pouch. Thus the sealing device has sealed the top of the filled pouch and sealed the bottom of the next pouch to be formed, all in one operation. The filling of the product may be conducted on a continuous or intermittent basis. One such vertical form, fill and seal machine of the type described above is sold under the trade-mark PREPAC. Other suitable machines are sold under the trade-marks INPACO and ELECSTER.
A variety of flowable materials may be packaged in this manner, for example, milk, syrups, sauces, juices, water and the like. The term “flowable material” can include materials that are flowable under gravity or may be pumped. Such materials may include emulsions, pastes, peanut butter, preserves, dough, ground meat, powders, detergents, oils and granular solids. Such pouches can also be used to contain other flowable materials such as foods that are packaged under sterile, pasteurized or aseptic conditions. The packaging conditions will normally require modifications to the machine and also modifications to the methods of packaging.
The pouches produced through this type of process can be manufactured to contain any volume of flowable material. In the situation where drinking fluids are packaged in this fashion, a typical size might be 250 mls or 500 mls. In such instance, it is possible to consume the fluid directly from the pouch. Thus, providing a pouch that includes an easy-open feature for this purpose is desirable especially when served in correctional facilities since it avoids the necessity to use an implement such as a knife or scissors. In addition, since these packages are meant for one-time use and are disposable, it is appropriate that the manner in which they are manufactured is as economical as possible, without sacrificing the basic packaging requirements for the materials in question.
Many solutions have been proposed for producing packages of this type, and typically such packages have included a notch or tear line which allows the package to be opened. For example, French Patent No. 1 216 422 discloses liquid-filled polymer pouches that are produced by collapsing a tube and having an easy-open feature. The easy-open feature comprises a sealed area partially extending across the width of the pouch and a weakened line extending within the sealed area. The weakened line is formed using a set of jaws where one jaw comprises a piano wire.
United Kingdom Patent No. 898,641 discloses a pouch having a line of weakness for easy opening that is produced by pressing the sheet between a solid plate and a ribbed die while heat is applied. The sheet is pinched between the plate and the rib of the die and reduced in thickness but not sheared, or otherwise punctured along the desired line.
U.S. Pat. No. 5,038,550 and European Patent No. 0 372 886 both disclose pouches having a slit formed within a sealed portion. The slit is intended as a device for starting a tear and for directing the tear in a preferred direction. In both cases the sealed portion is formed first using a sealing element and then the slit is formed using a separate cutting operation using a knife.
U.S. Patent Application Publication No. US 2006/0110081 A1 published on May 25, 2006, discloses a pouch for containing a flowable material, provided with an easy-open feature located adjacent to an upper closure or a lower closure of the pouch. The easy-open feature comprises a seal formed between two layers of film and provides a tear line for opening the pouch and tearing a corner off the pouch.
One concern with easy-open features in packaging pouches is that during the production, filling, handling or any manipulation of the pouches, stresses are induced in the film that forms the walls of the pouch. Therefore, depending on the configuration of the easy-open feature, it may produce a stress concentration in the film and hence make the film more susceptible to tearing in specific areas.
Thus there is a need for an improved heat sealing jaw that can be used to easily and economically produce an easy-open feature in a pouch that is sufficiently robust to withstand stresses induced on the pouch during manipulation and/or filling of the pouch.